Development of Childhood Obesity and High-risk Behavior Engagement in Adolescence Abstract Childhood obesity and high-risk behaviors in adolescence (e.g., illicit drug use and delinquency) are major social issues facing the nation. Childhood obesity is associated with many and various adverse health and psychological consequences (e.g., asthma and low self-esteem). Developmental trajectories of childhood obesity and their relationship to the incidence of both concurrent and subsequent problem behaviors, especially in adolescence, have not yet been well established, in large part because prospective longitudinal studies are rarely available. Yet systematic examination of developmental patterns of obesity in children and a better understanding of the relationship of such patterns to problem behaviors have important implications for improving youth intervention programs for a variety of problematic behaviors. The proposed project is a prospective longitudinal study that examines such issues among children as they transition to adolescence and to young adulthood. Drawing upon key concepts from a well-established psychosocial model for adolescent risk behaviors and based on the child sample derived from the 1979 National Longitudinal Survey of Youth (NLSY79), the proposed study will utilize measures of body mass index (BMI) over time to identify developmental trajectories of BMI among children throughout their childhood (ages 2 to 18), examine the role of mothers' characteristics on the development of high percentiles of BMI, and investigate associations of BMI- percentile trajectories with the development of high-risk behaviors from adolescence to young adulthood (ages 14 to 23). The study's specific aims are to: (1) depict developmental trajectories of BMI percentiles from ages 2 to 18, examine the incidence of high percentiles of BMI during childhood, and identify distinctive patterns of trajectories of BMI percentiles; (2) examine whether and how trajectories of BMI percentiles are associated with the development and maintenance of high-risk behaviors from ages 14 to 23; (3) identify mothers' characteristics and history of problem behaviors (e.g., smoking, alcohol and drug use, delinquency) associated with the development of high percentiles of BMI among their children; and (4) describe gender and ethnic differences in factors and processes resulting from the above aims. PUBLIC HEALTH RELEVANCE: Using the child sample from the NLSY79, this study will identify distinctive trajectory patterns of BMI percentiles during childhood and examine how such patterns are associated with smoking, alcohol consumption, drug use, and delinquency in adolescence. Study results will have implications for developing improved prevention and intervention strategies for obesity and risk-related behaviors among children and adolescents, with a specific emphasis on substance use.